Pine beetles bore their way through the hard exterior of a tree into the innermost layer of the bark called the phloem. The phloem is a crucial component of the tree because it carries water and nutrients to all parts of the plant.

 

Once the beetle has made its way inside, it lays eggs in the phloem.  After the eggs hatch, the larvae remain under the bark feeding on the phloem.

 

In response, the tree will attempt to drown the beetles by increasing the production of sap. To block the tree’s sap production, the larvae release a fungus called ‘blue stain fungi.’ In addition to keeping the larvae safe from the sap, the fungus also stains the tree blue.

 

After about two weeks of infestation by pine beetles, a tree usually dies from the damage to the phloem.  

 

The larvae spend the winter inside the bark and transform into pupae in late spring. Once they grow into adults, the pine beetles emerge from the infested tree over the course of the summer and early fall.

 

They can be found mostly in western North America from Mexico to British Columbia. The pine beetles have been known to attack ponderosa, lodgepole, Scotch and limber pine trees.

 

Several forests through North America have experienced severe pine beetle outbreaks in recent years. Large swaths of trees in British Columbia, Alberta and Colorado have been hit hard with pine beetle infestations since 2006.

 

Sources:

• “Mountain Pine Beetle” via Colorado State University Extension

• “Beetle Facts” via British Columbia Ministry of Forest, Mines and Lands

• “Bark Beetles Kill Millions of Acres of Trees in West” via New York Times